Validate::is to handle array input. Simplify Validation using the new feature.
replace the code for array/single value. less indent.
closure filter to pass ValueTO object to manage value, error, message, and even loop.
(was just passing a value. OK for just a filter not good for validations).
addCustom and custom{,2,3} filter name slot. write about custom filter.
rename choice rule as in rule. conform to the documentation.
test custom multiple rule.